opts2struct

A C macro with helper functions for creating an opts struct from argv

Usage

• Step 1: provide your option names, defaults, and short names in myopts2struct.h:

  OPTS2STRUCT(key1, key2, key3, ... , keyN)

  OPTS2STRUCT(default_val1, default_val2, default_val3, ..., default_valN)

  OPTS2STRUCT(shortkey1, shortkey2, shortkey3, ..., shortkeyN)

  • this file is treated as a config file and is in .gitignore so it isn't tracked.
  • make a copy of myopts2struct.h.example to start. Note that you also need to set OPTS2EMPTY in there.

• Step 2: call helper functions to initialize and then parse argv[]:

  struct opts2struct_t *ops2s = opts2struct_create();

  opts2struct_parseopts(ops2s, argc, argv);

  • this step is optional if you'd rather do the parsing yourself, but then the entire thing is optional, isn't it?

Details

After calling opts2struct_create() in Step 2 above, you'll have auto-generated structure field names in ops2s, as well as enums matching the names of your keys for accessing the same options using an array. You'll also have names[], defaults[], and shortnames[] arrays containing your field names, defaults, and shortnames as C strings.

After supplying opts2struct_parseopts() with the argv C string array of --key=value, --key, or --nokey items (there can be 0 or more dashes to start the key name within the input) or -k value, -k true, or -nok you'll have:

• ops2s->found[] to see which options were found on the command line
• ops2s->argtypes[] to get their type (C string, integer, floating point, or boolean in the case of --[no]key)
• ops2s->i[] and ops2s->as_int-> to access integer-valued options (or boolean, which have 0 and 1 integer values)
• ops2s->f[] and ops2s->as_float-> to access floatingpoint-valued options (as well as pre-promoted integers and booleans)
• ops2s->v[] and ops2s-> to access values in their original string form, split off from argv (or true and false in the case of boolean flag input)

Defaults and Short Names

`OPTS2DEFAULTS(default1, default2, ..., defaultN)` and
`OPTS2SHORTNAMES(shortname1, shortname2, ..., shortnameN)`

• allow setting default values for keys not provided by user
• shortnames can be provided with spaces rather than equal signs between key and value
  • e.g., -s 3 (the single hyphen is required, unlike the key=value form)
• N above must be equal to the number of options in the OPTS2STRUCT macro
• all three macro settings should be made in myopts2struct.h

Example

See the example.c file for an example.

Run make test to run a set of different command-line invocations, demonstrating defaults, short names, and bool flags.

Limitations:

• opts2struct is intentionally simple, and is not meant to replace getopt
• probably incompatible with Visual C++, but should work with minor tweaks
  • opts2struct.h uses named variadic macros (a GNU extension to C99 always-named-__VA_ARGS__ variadic macros) and anonymous structs and unions, which are part of the C11 standard and a GNU extension prior to that (for unions anyway).

The following limitations apply to the helper functions:

• no attempt to differentiate between option and non-option area of command-line (ie no --), but args not listed in OPTS2STRUCT macro will be ignored
• required supplying default values and shortnames, and creates static global counterparts
  • the only way to bypass them is to ifdef out the lines that refer to them
  • next todo item is different levels of "buy-in"
• workaround: just copy the OPTS2STRUCT macro to a new file and use that alone
  • perhaps remove the fields for names, defaults, and shortnames if not desired
  • do your own parsing etc.